Katia Davis says an after-school teacher at Detroit's Drew Elementary bullied her 9-year-old son, slamming his head against a desk and causing a mild concussion.

Davis says her son came home last weekend with a large knot on the back of his head and told her his teacher was to blame.

"I was just talking to Brianna about singing some kind of song, and that's when she just came over there, wrapped her hands around my neck and slammed my head against a desk," the student, Charles Davis, told Fox 2.

Davis says she confronted the teacher after hearing her son's story.

"And I asked her, 'Well, did you do that to my child?' And she was like, 'Yeah, because he wouldn't sit down, and I was just really frustrated and I apologize.' And that's when I told her I'll let the police deal with you," said Katia Davis.

School administrators told Davis they would deal with the situation, but she called police anyway, and officers arrested the teacher.

Davis took her son to the hospital, where she says he was treated for a mild concussion.

Fox 2 reports Detroit police have handed the case over to the Wayne County Prosecutor's Office for further investigation. It's not clear if or when charges will be filed.

Detroit Public Schools has fired the vendor that operated the after-school program, and the accused teacher has been barred from Drew Elementary.